Ellipsometer

Description

[0001] The present invention relates to an ellipsometer for studying optical characteristics or film thickness of a sample by detecting a change in polarization of light, which has been plane-polarized before reflected by a surface of the sample.

[0002] The ellipsometer is an instrument or apparatus that studies optical characteristics or film thickness of a sample by basically causing plane-polarized light to be reflected at a surface of the sample and then measuring resultant elliptically-polarized light produced by the reflection.

[0003] There is a type of the ellipsometer, which causes plane-polarized light to be successively reflected by an objective sample to be measured and a reference sample as a criterion for comparison. Such ellipsometer is designed such that influences to the polarization by the respective reflections at the objective and reference sample surfaces are cancelled out when the optical characteristics of the surface of the objective sample are coincident with those of the reference sample. Since the ellipsometer detects difference in optical characteristics between the reference and objective sample surfaces, it has a relatively high sensitivity.

[0004] In the ellipsometer using the reference sample and the objective sample, both samples should be accurately positioned. In other words, both of the reference sample and the objective sample should be placed at appropriate positions and in appropriate orientations.

[0005] The most general manner for producing plane-polarized light having a specific plane of polarization is to cause nonpolarized light to pass through a polarizer, which allows light having a specific plane of polarization to transmit therethrough. In practice, the ellipsometer generally employ the plane-polarized light produced in this manner.

[0006] However, such ellipsometer has extremely low utilization ratio of light. More specifically, the ratio of light components transmitting through the polarizer to those incident upon the polarizer is very low. The low utilization ratio of light is a main reason why the ellipsometer enabling highly accurate measurement has not been attained.

[0007] An example of a prior art ellipsometer is disclosed in EP-A-982 580.

[0008] The present invention is defined in the appended claims.

[0009] The invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a plan view of an ellipsometer according to an embodiment of the present invention;

FIG. 2 is a perspective view of a turn-around prism shown in FIG. 1;

FIG. 3 is a perspective view of a sample holder unit shown in FIG. 1; and

FIG. 4 is a perspective view of the polarization angular adjusting mechanism shown in FIG. 1.

[0010] As shown in FIG. 1, according to an embodiment of the present invention, an ellipsometer 100 comprises a pair of sample holder units 112, 122 for holding two kinds of samples. For example, the sample holder unit 112 holds a reference sample 114, whereas the sample holder unit 122 holds an objective sample 124. The reference sample 114 is used as a criterion for comparison with the objective sample 124 in analyzing polarization.

[0011] Alternatively, the sample holder unit 112 may hold the objective sample in place of the reference sample, whereas the sample holder unit 122 may hold the reference sample in place of the objective sample. Such replacement produces no difference in optical characteristics and the measurement results. However, herein, the following explanation will be made on the assumption that the sample holder unit 112 holds the reference sample and the sample holder unit 122 holds the objective sample.

[0012] The reference sample holder unit 112 and the objective sample holder unit 122 are placed on an XY stage 108 on the base 102 so as to be displaced by the XY stage 108 in parallel to the upper surface of the base 102.

[0013] The ellipsometer 100 comprises a beam projecting portion 130 for projecting a light beam toward the reference sample 114, a polarizer 138 for allowing light having a specific plane of polarization to transmit therethrough, a turn-around prism 170 for turning around the light beam reflected from the reference sample 114 in parallel at a distance to direct it to the objective sample 124, an analyzer 140 for allowing light having a specific plane of polarization to transmit therethrough, and a light detector 150 for detecting light transmitted through the analyzer 140.

[0014] Furthermore, the ellipsometer 100 has a first optical path or forward optical path, which extends from the beam projecting portion 130 to the turn-around prism 170 through the reference sample 114, and a second optical path or backward optical path, which extends from the turn-around prism 170 to the light detector 150 through the objective sample 124. The first and second optical paths extend in parallel at a distance between them and coupled with each other through the turn-around prism 170.

[0015] The beam projecting portion 130 comprises a light source 132, an optical fiber 134, and an optical fiber fixing portion 136. The light source 132 may comprises a solid laser, gas laser, semiconductor laser, or dye laser. In use of the semiconductor laser as the light source, the beam projecting portion 130 should include a collimator.

[0016] The polarizer 138 is located on the forward optical path between the optical fiber fixing portion 136 and the reference sample 114. The analyzer 140 is located on the backward optical path between the objective sample 124 and the light detector 150.

[0017] Each of the polarizer 138 and the analyzer 140 preferably comprises a Glan-Thompson prism. The polarizer 138 and the analyzer 140 are arranged so that planes of polarization of light transmitted therethrough mutually intersect at right angles. In other words, the polarizer 138 and the analyzer 140 are arranged so as to satisfy crossed Nicols.

[0018] The polarizer 138 is angularly positioned so as to transmit light having a plane of polarization inclined by an angle of +45° with respect to a plane of incidence of the reference sample 114. The term "plane of incidence of the reference sample 114" used herein means a plane containing a normal to the wavefront incident on a surface of the reference sample 114, that is, a direction of propagation, and a normal to the sample surface.

[0019] The light detector 150 comprises a photodiode, APD, or photomultiplier, for example. In use of a multiwave light source, such as a xenon lamp or a halogen lamp is used, the light detector 150 should include a spectroscope.

[0020] The optical fiber fixing portion 136, the polarizer 138, analyzer 140, and light detector 150, all are mounted on a first support board 104. The first support board 104 is inclined at a predetermined angle with respect to the base 102. An incident angle of the plane-polarized light beam transmitted through the polarizer 138 with respect to the reference sample 114 is determined by the aforementioned predetermined angle.

[0021] The turn-around prism 170 is mounted on a second support board 106. The second support board 106 is inclined with respect to the base 102 by the same angle of the first support board 104 with respect to the base 102.

[0022] The turn-around prism 170 comprises three right-angle prisms 172, 174 and 176 cemented with each other, as shown in FIG. 2. The turn-around prism 170 reflects the beam four times within it so as to cause the turned-around beam to exit in parallel to the incident beam at a predetermined distance. The turn-around prism 170 is fixed on the second support board 106 inclined by an angle of 45° such that a plane containing axes of the incident and turned-around beams is in parallel to the surface of the second support board 106.

[0023] In FIG. 1, a light beam emitted from the light source 132 propagates within the optical fiber 134 and is projected from the optical fiber fixing portion 136. The light beam projected from the optical fiber fixing portion 136 passes through the polarizer 138 to be of plane-polarized light having a plane of polarization inclined by an angle of +45° with respect to the plane of incidence of the reference sample 114 and then reflected at a surface of the reference sample 114 mounted on the sample holder unit 112. The plane-polarized light is changed into elliptically polarized light by the reflection, the elliptically polarized light depending on optical characteristics, film thickness, or the like of the reference sample.

[0024] The elliptically polarized light beam is turned around by the turn-around prism 170 in parallel at a predetermined distance, reflected four times within it. The resultant elliptically polarized light has elliptical polarization whose major axis component and minor axis component are same in magnitude and direction (for example, major axis) but opposite in rotation direction to the elliptically polarized light before turned around.

[0025] The turned-around light beam from the turn-around prism 170 is reflected by the objective sample 124 mounted on the sample holder unit 122 to be directed to the analyzer 140. Since the analyzer 140 allows only the minor axis component of the elliptical polarization to transmit therethrough, the beam of only of the elliptical polarization is transmitted through the analyzer 140 and reaches the light detector 150.

[0026] If the light beam incident upon the light detector 150 has a multi-wavelength, it is spectroscopically treated and thereby photoelectrically transferred per wavelength. The electric signal output from the light detector 150 is supplied into a computer at which a predetermined arithmetic operation is performed. As a result, measurement data representing optical characteristics, film thickness, or the like are obtained.

[0027] When the reference sample 114 is the same as the objective sample 124, the effects of both samples upon the light beam are mutually cancelled out. A quenching phenomenon is resulted in which no light is detected by the light detector 150.

Sample Positioning Mechanism

[0028] For accurate detection of light with the light detector 150 in the ellipsometer 100, the reference sample 114 and the objective sample 124 must be located at appropriate positions and in appropriate orientations. As to the orientation, the height is particularly important. In other words, the reference sample 114 and the objective sample 124 must be located at appropriate heights and with appropriate inclinations. Therefore, the sample holder unit 112 can adjust the height and inclination of the reference sample 114 and the sample holder unit 122 can adjust the height and inclination of the objective sample 124.

[0029] The term "inclination", as used herein, refers a degree of anti-parallelism of the surface of the sample with respect to the upper surface of the base 102. The inclination can be decomposed into an inclination about a first axis, which is parallel to the upper surface and parallel to a projection of the forward optical path or the backward optical path onto the upper surface of the base 102, and an inclination about a second axis, which is parallel to the upper surface and perpendicular to the projection of the forward optical path or the backward optical path onto the upper surface of the base 102. The "height", as used herein, refers the position along a third axis perpendicular to the upper surface of the base 102. Hereinafter, the first, second, and third axes are referred to as an X-, Y-, and Z-axes, respectively.

[0030] The reference sample holder unit 112 and objective sample holder unit 122 have the same structure. Each unit comprises a sample holder 182, a goniostage 192 for inclining the sample holder 182 about the X-axis, a goniostage 194 for inclining the sample holder 182 together with the goniostage 192 about the Y-axis, and a height adjusting stage 196 for displacing the sample holder 182 together with the two goniostages 192 and 194 along the Z-axis, as shown in FIG. 3.

[0031] The sample holder 182 has a recess 184 for containing a sample and three support portions 186, formed in the recess, for supporting the sample. Each of the support portions 186 has a suction port 188, which is communicated with a suction system 190. When the suction port 72 is sucked by means of the suction system 190, the samples is vacuum-fixed on three support portions 186 due to negative pressure.

[0032] The goniostage 192 has a rotatable input axis 192a for adjusting the inclination such that the sample holder 182 is inclined about the X-axis on rotating the input axis 192a. The goniostage 194 has a rotatable input axis 194a for adjusting the inclination such that the sample holder 182 is inclined about the Y axis on rotating the input axis 194a. The height adjusting stage 196 has a rotatable input axis 196a for adjusting the height such that the holder 182 is displaced along the Z-axis on rotating the input axis 196a.

[0033] The two sample holder units 112 and 122 and the height adjusting stage 196 may be integrated into one body. In other words, both the sample holder 182, the goniostages 192, 194 of the reference sample holder unit 112 and those of the objective sample holder unit 122 may be arranged on a single height adjusting stage 196.

[0034] The ellipsometer 100 has a sample positioning mechanism for adjusting the heights and inclinations of the reference sample 114 and the objective sample 124. The sample positioning mechanism includes the two sample holder units 112 and 122. In addition to these, the sample positioning mechanism has a height/inclination adjusting section 300 for the reference sample and a height/inclination adjusting section 400 for the objective sample.

[0035] The height/inclination adjusting section 300 has a height-measuring CCD unit 310, an inclination-measuring CCD unit 320, and a processing portion 330 for processing data obtained by the CCD units 310 and 320.

[0036] The height measuring CCD unit 310 has a mirror 312 for deflecting the light beam as needed, a rotary 314 for moving the mirror 312 between a position crossing the optical path and a position off the optical path, and a CCD camera 316 for taking a picture of the light beam deflected by the mirror 312.

[0037] The height measuring CCD unit 320 has a mirror 322 for deflecting the light beam as needed, and a rotary 324 for moving the mirror 322 between a position crossing an optical path and a position off the optical path, an objective lens 326 for converging the light beam deflected by the mirror 322, and a CCD camera 328 for taking a picture of the light beam converged by the objective lens 326.

[0038] In FIG. 1, the height measuring CCD unit 310 is positioned upstream of the direction of propagation of the beam, whereas the inclination measuring CCD unit 320 is positioned downstream thereof. These CCD units may be arranged oppositely. In other words, it may be possible that the height measuring CCD unit 320 is positioned upstream, whereas the height measuring CCD unit 310 is positioned downstream.

[0039] Similarly, the height/inclination adjusting section 400 of the objective sample includes a height measuring CCD unit 410, an inclination measuring CCD unit 420, and a processing portion 430 for processing data obtained by these CCD units 410 and 420.

[0040] The height measuring CCD unit 410 has a mirror 412 for deflecting the light beam as needed, and a rotary 414 for moving the mirror 412 between a position crossing an optical path and a position off the optical path, and a CCD camera 416 for taking a picture of the light beam deflected by the mirror 412.

[0041] The inclination measuring CCD unit 420 has a mirror 422 for deflecting the light beam as needed, and a rotary 424 for moving the mirror 422 between a position crossing an optical path and a position off the optical path, an objective lens 426 for converging the light beam deflected by the mirror 422, and a CCD camera 428 for taking a picture of the light beam converged by the objective lens 426.

[0042] In FIG. 1, the height measuring CCD unit 410 is positioned upstream of the direction of propagation of the beam, whereas the inclination measuring CCD unit 420 is positioned downstream thereof. These CCD units may be arranged oppositely. In other words, it may be possible that the inclination measuring CCD unit 420 is positioned upstream, wherein the height measuring CCD unit 410 is placed downstream.

[0043] The height and inclination of the reference sample 114 may be manually or automatically performed.

[0044] In order to manually adjust the height and inclination of the reference sample 114, the processing portion 330 has a monitor for displaying an image of a spot of the light beam in the picture obtained by the CCD camera 316 of the height measuring CCD unit 310 and an image of a spot of the converged light beam in the picture obtained by the CCD camera 328 of the inclination measuring CCD unit 320.

[0045] The height and inclination are adjusted as follows. First, the mirror 312 of the height measuring CCD unit 310 is placed at the position across the optical path so that the image of the spot of the light beam in the picture obtained by the CCD camera 316 is displayed on the monitor. While viewing the display, an operator manually operates the input axis 196a of the height adjusting stage 196 to adjust the height adjusting stage 196 so as to position a center of the gravity of the spot image at an appropriate position, for example, at the center. After the adjusting, the mirror 312 is returned to the position off the optical path.

[0046] Subsequently, the mirror 322 of the inclination measuring CCD unit 320 is placed at the position across the optical path so that the image of the spot of the converged light beam in the picture obtained by the CCD camera 328 is displayed on the monitor. While viewing the display, the operator manually operates the input axes 192a, 194a of the goniostages 192, 194 to adjust the goniostages 192, 194 so as to place the image of the converged spot at an appropriate position, for example, the center position. After the adjusting, the mirror 312 is returned to a position off the optical path.

[0047] On the other hand, in order to automatically adjust the height and inclination of the reference sample 114, the processing portion 330 includes an arithmetic calculation means for obtaining data of height and inclination of the reference sample 114, a driving means for driving the input axis 192a of the goniostage 192, the input axis 194a of the goniostage 194, and the input axis 196a of the height adjusting stage 196, and a control means for controlling the driving means in accordance with the data of height and inclination.

[0048] The arithmetic calculation means converts an image of a spot of the light beam in the picture obtained by the CCD camera 316 of the height measuring CCD unit 310 into binary form to obtain a center of gravity of the spot, and also obtains inclination data on the basis of a position of an image of a spot of the converged light beam in the picture obtained by the CCD camera 328 of the inclination measuring CCD unit 320.

[0049] The driving means includes, for example, three stepping motors, which have rotation shafts connected directly or indirectly through members such as rubber or belts to the input axis 192a of the goniostage 192, the input axis 194a of the goniostage 194, and the input axis 196a of the height adjusting stage 196, respectively.

[0050] The height and inclination of the reference sample 114 are adjusted as follows. First, the mirror 312 of the height measuring CCD unit 310 is placed at the position crossing the optical path. The arithmetic calculation means obtains the height data based on the position of the center of gravity of the image of the spot in the picture obtained by the CCD camera 316. The control means controls the driving means with the height data at an appropriate value such that the height adjusting stage 196 is correctly adjusted. After the adjustment, the mirror 312 is returned to the position off the optical path.

[0051] Then, the mirror 322 of the inclination measuring CCD unit 320 is placed at the position crossing the optical path. The arithmetic calculation means obtains the inclination data based on the position of the image of the spot of the converged light beam in the picture obtained by the CCD camera 328. The control means controls the driving means with the inclination data at appropriate values such that the goniostages 192, 194 are correctly adjusted. After the adjustment, the mirror 322 is returned to a position off the optical path.

[0052] In the present embodiment, the height is adjusted first and then, the inclination is adjusted. However, the height and inclination may be adjusted in a reverse order. More specifically, it may be possible that the inclination is adjusted first and then the height is adjusted.

[0053] In the same manner as in the reference sample 114, the height and inclination of the objective sample 124 may be manually or automatically adjusted.

[0054] In order to manually adjust the height and inclination of the objective sample 124, the processing portion 430 has a monitor for displaying an image of a spot of the light beam in the picture obtained by the CCD camera 416 of the height measuring CCD unit 410 and an image of a spot of the converged light beam in the picture obtained by the CCD camera 428 of the inclination measuring CCD unit 420.

[0055] The height and inclination are adjusted as follows. First, the mirror 412 of the height measuring CCD unit 410 is placed at the position crossing the optical path so that the image of the spot of the light beam in the picture obtained by the CCD camera 416 is displayed on the monitor. While viewing the monitor, an operator manually operates the input axis 196a of the height adjusting stage 196 to adjust the height adjusting stage 196 so as to place a center of the gravity of the spot image at an appropriate position, for example, at the center. After the adjustment, the mirror 412 is returned to the position off the optical path.

[0056] Subsequently, the mirror 422 of the inclination measuring CCD unit 420 is placed to the position crossing the optical path so that the image of the spot of the converged light beam in the picture obtained by the CCD camera 428 is displayed on a monitor. While viewing the monitor, the operator manually operates the input axes 192a, 194a of the goniostages 192, 194 to adjust the goniostages 192, 194 so as to place the image of the converged spot at an appropriate position, for example, at the center. After the adjustment, the mirror 422 is returned to the position off the optical path.

[0057] On the other hand, in order to automatically adjust the height and inclination of the objective sample 124, the processing portion 430 includes an arithmetic calculation means for obtaining data of height and inclination of the objective sample 124, a driving means for rotating the input axis 192a of the goniostage 192, the input axis 194a of the goniostage 194, and the input axis 196a of the height adjusting stage 196, and a control means for controlling the driving means in accordance with the data of height and inclination.

[0058] The arithmetic calculation means converts an image of a spot of the light beam in the picture obtained by the CCD camera 416 of the height measuring CCD unit 410 into binary form to obtain a center of gravity of the spot, and also obtains inclination data on the basis of a position of an image of a spot of the converged light beam in the picture obtained by the CCD camera 428 of the inclination measuring CCD unit 420. The driving means includes, for example, three stepping motors, which have rotation shafts connected directly or indirectly through members such as rubber or belts to the corresponding input axes.

[0059] The height and inclination of the objective sample 124 are adjusted as follow. The mirror 412 of the height measuring CCD unit 410 is placed at the position crossing the optical path. The arithmetic calculation means obtains the height data based on the position of the center of gravity of the image of the spot in the picture obtained by the CCD camera 416. The control means controls the driving means with the height data at an appropriate value such that the height adjusting stage 196 is correctly adjusted. After the adjustment, the mirror 412 is returned to the position off the optical path.

[0060] Then, the mirror 422 of the inclination measuring CCD unit 420 is placed at the position crossing the optical path. The arithmetic calculation means obtains the inclination data based on the position of the image of the spot of the converged light beam in the picture obtained by the CCD camera 428. The control means controls the driving means with the inclination data at appropriate values such that the goniostages 192, 194 are correctly adjusted. After the adjustment, the mirror 422 is returned to the position off the optical path.

[0061] In the present embodiment, the height is adjusted first and then, the inclination is adjusted. However, the height and the inclination may be adjusted in a reverse order. More specifically, it may be possible that the inclination is adjusted first and then the height is adjusted.

[0062] The ellipsometer 100 of the present embodiment has the sample positioning mechanism for adjusting the height and inclination of the reference sample 114 and the objective sample 124. The highly reproducible and accurate measurement can be performed.

Polarization Angular Adjusting Mechanism

[0063] In the ellipsometer 100, the light incident upon the polarizer 138 is preferably a plane-polarized light having the same plane of polarization as that of the plane-polarized light that the polarizer 138 allows to transmit. Therefore, as for the beam projecting portion 130, the light source 132 preferably emits a plane-polarized light and the optical fiber 134 comprises a polarization-preserving fiber, which is fixed to the optical fiber fixing portion 136 so that the plane of polarization of the plane-polarized light projected from the polarization-preserving fiber is the same as that of the plane-polarized light that the polarizer 138 allows to transmit.

[0064] The optical fiber 134, not limited to the polarization-preserving fiber, is required to be fixed to the optical fiber fixing portion 136 at a right position on a plane perpendicular to the optical axis and with a right orientation so that the light is appropriately detected by the light detector 150. These requirements are stringent in assembling the apparatus. In addition to them, it is very difficult to appropriately adjust the angular orientation or angle about the optical axis of polarization-preserving fiber 134 as mentioned above.

[0065] The ellipsometer 100 has a polarization angular adjusting mechanism 200 for adjusting the angle of the plane of polarization of the beam projected from the beam projecting portion 130 about the optical axis, in order to satisfy the requirements for using light efficiently, in other words, to cause the plane-polarized light having the same plane of polarization as the light that the polarizer 138 allows to transmit to enter the polarizer 138, without requiring stringent requirements in assembling the apparatus.

[0066] The polarization angular adjusting mechanism 200, which is arranged between the beam projecting portion 130 and the polarizer 138, comprises a plane-polarized light rotating element 202 rotatably supported about the optical axis. As the plane polarization rotation element 202 used herein, any optical element may be used as long as it is rotates a plane of polarization of incident plane polarized light.

[0067] The plane polarization rotational element 202, which comprises a half-wave plate, for example, converts the incident plane-polarized light having the plane of polarization with an angle of θ with respect to the optic axis into the plane-polarized light having the plane of polarization with an angle of 2θ with respect to the optic axis. When the half-wave plate is rotated so that the direction of the optic axis of the half-wave plate is changed within a range of 0 to 180° with respect to the plane of polarization of the incident plane-polarized light, the plane of polarization of the light transmitted through the plate is varied within a range of 0 to 360°. That is, the angular orientation or angle of the plane of polarization of the light transmitted through the half-wave plate can be changed by rotating the half-wave plate.

[0068] The polarization angular adjusting mechanism 200 has a mount 210 for rotatably supporting the plane polarization rotatory element 202, as shown in FIG. 4. The mount 210 has a movable frame for holding the plane polarization rotatory element 202 and a fixed frame 214 for supporting the movable frame 212 rotatably about the axis 216, which is coincident with the optical axis. The fixed frame 214 may have an angular adjusting mechanism for adjusting an angle of the movable frame 212 about the axis 216, such that the angular adjusting mechanism, which has a rotatable input axis, converts the rotation of the input axis into a relatively minute angular change of the movable frame.

[0069] The angular orientation or angle of the plane polarization rotatory element 202 about the optical axis is, for example, manually adjusted as follows. While monitoring the output from detection means for detecting the light transmitted through the polarizer 138, an operator rotates the input axis of the angular adjusting mechanism of the fixed frame 214 by hand to set the angle of the movable frame 212 so as to obtain a maximum output from the detection means. After the adjustment, the movable frame 212 is fixed on the fixed frame 214 by means of, for example, a screw.

[0070] Alternatively, the angular orientation or angle of the plane polarization rotatory element 202 about the optical axis may be automatically adjusted. The polarization angular adjusting mechanism 200 further comprises a control section 220 for controlling the polarization angular adjusting mechanism. The control section 220 comprises, for example, driving means for rotating the input axis of the angular adjusting mechanism, detection means for detecting light transmitted through the polarizer 138, and control means for controlling the driving means on the basis of the output from the detection means. The control means controls the driving means so as to obtain a maximum output from the detection means. The driving means has also a function of fixing the movable frame 212 to the fixed frame 214 after the control. The driving means includes, for example, a stepping motor, which has a rotation shaft connected directly or indirectly through a member such as rubber or belt to the input axis of the angular adjusting mechanism.

[0071] The detection means mentioned above for detecting light transmitted through the polarizer 138 comprises, for example, a light receiving element inserted on the optical path between the polarizer 138 and the analyzer 140. Alternatively, the detection means may comprise a deflection element such as mirror inserted on the optical path between the polarizer 138 and the analyzer 140 and a light receiving element for receiving the light deflected by the mirror. Moreover, the detection means may be the light detector 150 with the polarizer 140 eliminated from the optical path.

[0072] Since the ellipsometer 100 of the present embodiment comprises the polarization angular adjusting mechanism 200, which can arbitrarily change the orientation or angle of the plane of the polarization of the beam incident upon the polarizer 138, the ellipsometer 100 can easily cause the plane of polarization of the plane-polarized light incident upon the polarizer to match with the transmission or optic axis of the polarizer. Therefore, it is possible to attain efficient utilization of light and efficiently improve accuracy in measurement.

[0073] The ellipsometer 100 according to this embodiment may be modified in various ways. Although the reference sample 114 may be exchangeable in the aforementioned embodiments, it may be non-exchangeable. In a preferable ellipsometer 100 employing non-exchangeable reference sample 114, the reference sample 114 is fixed at an appropriate position determined in advance. In this case, the height/inclination adjusting section 300 for the reference sample is not required. Therefore, the apparatus may be equipped with only the height/inclination adjusting section 400 for the objective sample.

[0074] Furthermore, the ellipsometer 100 may comprise a CCD camera unit for taking a picture of the reference sample 114 and the objective sample 124 from above, to adjust the positions of the reference sample 114 and the objective sample 124 in the horizontal direction (direction parallel to a plane containing the X-axis and Y-axis). Furthermore, to automatically adjust the positions in the horizontal direction, the ellipsometer 100 may have a mechanism for adjusting an XY stage based on the data obtained by the CCD camera unit.

[0075] The beam projecting portion 130 may project the light beam emitted from the light source 132 directly toward the reference sample 114 without passing through the optical fiber. In this case, the beam projecting portion 130 has a light source fixing portion in place of the optical fiber fixing portion.

Claims

1. An ellipsometer (100) for detecting polarization of light successively reflected from a reference sample and an objective sample to study a surface state of the objective sample, the ellipsometer, which has a first optical path and a second optical path, comprising:

a first sample holder unit (112) for holding a first sample (114);

a second sample holder unit (122) for holding a second sample (124);

a beam projecting portion (130) for projecting a beam of plane-polarized light toward the first sample;

a polarizer (138) for allowing light having a specific plane of polarization to transmit therethrough;

a turn-around prism (170) for turning around the light beam reflected from the first sample in parallel at a distance to direct it to the second sample;

an analyzer (140) for allowing light having a specific plane of polarization to transmit therethrough; and

a light detector (150) for detecting light transmitted through the analyzer,

the first optical path extending from the beam projecting portion (130) to the turn-around prism (170) by way of the first sample (114), the second optical path extending from the turn-around prism (170) to the light detector (150) by way of the second sample (124), the first and second optical paths extending in parallel at an interval between them and communicated with each other through the turn-around prism (170);

the polarizer (138) located on the first optical path between the beam projecting portion (130) and the first sample (114), the analyzer (140) located on the second optical path between the second sample (124) and the light detector (150), the polarizer (138) allowing plane-polarized light having a plane of polarization inclined at an angle of +45° with respect to a plane of incidence of the first sample to transmit therethrough, the polarizer (138) and analyzer (140) satisfying crossed Nicols;

one (124) of the first and second samples being the objective sample, the other (114) of the first and second samples being the reference sample to be compared to the objective sample in polarization analysis, accordingly, one (122) of the first and second sample holder units being an objective sample holder unit, the other (112) one of the first and second sample holder units being a reference sample holder unit;

a sample positioning mechanism (310, 320, 330, 410, 420, 430) for arranging the first and second samples at appropriate positions and in appropriate orientations, the sample positioning mechanism including the objective sample holder unit (122), the objective sample holder unit holding the objective sample (124) so as to adjust height and inclination thereof, and the sample positioning mechanism comprising an objective sample height/inclination adjusting section (410, 420, 430) for adjusting the height and inclination of the objective sample;
said ellipsometer further comprising a polarization angular adjusting mechanism (200), arranged between the beam projecting portion (130) and the polarizer (138), for adjusting angular direction of the polarization of plane-polarized light about an optical axis projected from the beam projecting portion (130), the polarization angular adjusting mechanism (200) comprising a plane-polarization rotatory element (202) for rotating the polarization of incident plane-polarized light about the optical axis, and a mount (210) for rotatably supporting the plane-polarization rotatory element (202) about the optical axis.

2. The ellipsometer according to claim 1, wherein the objective sample holder unit (122) comprises a sample holder (182) on which the objective sample is fixed, a first goniostage (192) for inclining the sample holder about a first axis, a second goniostage (194) for inclining the sample holder together with the first goniostage about a second axis, and a height adjusting stage (196) for displacing the sample holder together with the first and second goniostages along a third axis.

3. The ellipsometer according to claim 2, wherein the objective sample height/inclination adjusting section comprises a height-measuring optical unit (410), an inclination-measuring optical unit (420), and a processing section (430) for processing data obtained from each of the height-measuring optical unit and the inclination-measuring optical unit; the height-measuring optical unit (410) comprising a mirror (412) for deflecting the light beam as needed, a rotary (414) for moving the mirror between a position crossing the optical path and a position off the optical path, and a camera (416) for taking a picture of the deflected light beam from the mirror; and the inclination-measuring optical unit (420) comprising a mirror (422) for deflecting the light beam as needed, a rotary (424) for moving the mirror between a position crossing the optical path and a position off the optical path, an objective lens (426) for converging the deflected light beam from the mirror, and a camera (428) for taking a picture of the converged light beam by the objective lens.

4. The ellipsometer according to claim 3, wherein the processing section (430) has a monitor for displaying a spot of the light beam in the picture obtained by the camera of the height-measuring optical unit and displaying an image of a spot of the converged light beam in the picture obtained by the camera of the inclination-measuring optical unit.

5. The ellipsometer according to claim 3, wherein the processing section (430) comprises arithmetic calculation means for obtaining height/inclination data of the objective sample, driving means for rotating an input axis (192a) of the first goniostage (192), an input axis (194a) of the second goniostage (194), and an input axis (162a) of the height adjusting stage (196), and control means for controlling the driving means on the bases of the height/inclination data.

6. The ellipsometer according to claim 5, wherein the arithmetic calculation means obtains height data by converting an image of a spot of the beam in the picture obtained by the camera of the height-measuring optical unit into binary form to obtain a center of gravity of the image of the spot, and obtains inclination data on the basis of a position of an image of the spot of the converged beam in the picture obtained by the camera of the inclination-measuring optical unit.

7. The ellipsometer according to any one of claims 1 to 6, wherein the sample positioning mechanism includes the reference sample holder unit (112), the reference sample holder unit holding the reference sample (114) so as to adjust the height and inclination thereof, and the sample positioning mechanism comprises a reference sample height/inclination adjusting section (310, 320, 330) for adjusting height/inclination of the reference sample.

8. The ellipsometer according to claim 7, wherein the reference sample holder unit (112) comprises a sample holder (182) on which the reference sample is fixed, a first goniostage (192) for inclining the sample holder about a first axis, a second goniostage (194) for inclining the sample holder together with the first goniostage about a second axis, and a height adjusting stage (196) for displacing the sample holder together with the first and second goniostages along a third axis.

9. The ellipsometer according to claim 8, wherein the reference sample height/inclination adjusting section comprises a height-measuring optical unit (310), an inclination-measuring optical unit (320), and a processing section (330) for processing data obtained from each of the height-measuring optical unit and the inclination-measuring optical unit; the height-measuring optical unit (310) comprising a mirror (312) for deflecting the light beam as needed, a rotary (314) for moving the mirror between a position crossing the optical path and a position off the optical path, and a camera (316) for taking a picture of the deflected light beam from the mirror; and the inclination-measuring optical unit (320) comprising a mirror (322) for deflecting the light beam as needed, a rotary (324) for moving the mirror between a position crossing an optical path and a position off the optical path, an objective lens (326) for converging the deflected light beam from the mirror, and a camera (328) for taking a picture of the converged light beam by the objective lens.

10. The ellipsometer according to claim 9, wherein the processing section (330) has a monitor for displaying a spot of the light beam in the picture obtained by the camera of the height-measuring optical unit and displaying an image of a spot of the converged light beam in the picture obtained by the camera of the inclination-measuring optical unit.

11. The ellipsometer according to claim 9, wherein the processing section (330) comprises arithmetic calculation means for obtaining height and inclination data of the reference sample, driving means for rotating an input axis (192a) of the first goniostage (192), an input axis (194a) of the second goniostage (194), and an input axis (196a) of the height adjusting stage (196), and control means for controlling the driving means on the bases of the height and inclination data.

12. The ellipsometer according to claim 11, wherein the arithmetic calculation means obtains height data by converting an image of a spot of the light beam in the picture obtained by the camera of the height-measuring optical unit into binary form to obtain a center of gravity of the image of the spot, and obtains inclination data on the basis of a position of an image of the spot of the converged light beam in the picture obtained by the camera of the inclination-measuring optical unit.

13. The ellipsometer according to any of claims 1-12 wherein the plane polarization rotatory element (202) comprises a half-wave plate.

14. The ellipsometer according to claim 13, wherein the mount (210) rotates the half-wave plate (202) so that an angular direction of an optic axis of the half-wave plate is varied within a range of 0° to 180° with respect to the polarization of the incident plane-polarized light.

15. The ellipsometer according to any one of claims 1 to 14, wherein the mount (210) comprises a movable frame (212) for holding the plane-polarization rotatory element, and a fixed frame (214) for rotatably supporting the movable frame about an axis (216) identical to the optical axis.

16. The ellipsometer according to claim 15, wherein the fixed frame (214) comprises an angular adjusting mechanism for adjusting an angle of the movable frame about the axis, the angular adjusting mechanism having a rotatable input axis with a rotation supplied thereto converted into an angular change of the movable frame.

17. The ellipsometer according to claim 16, further comprising a control section (220) for controlling an angular adjusting mechanism, the control section comprising driving means for rotating the input axis of the angular adjusting mechanism, detection means for detecting light transmitted through the polarizer, and control means for controlling the driving means based upon output from the detection means so as to obtain a maximum output from the detection means.

Ansprüche

1. Ellipsometer (100) zur Erfassung einer Polarisation eines Lichts, das aufeinanderfolgend von einer Referenzprobe und einer Zielprobe reflektiert wird, um einen Oberflächenzustand der Zielprobe zu untersuchen, wobei das Ellipsometer, welches einen ersten Strahlengang und einen zweiten Strahlengang besitzt, umfasst:

- eine erste Probenhaltereinheit (112) zum Halten einer ersten Probe (114);

- eine zweite Probenhaltereinheit (122) zum Halten einer zweiten Probe;

- einen Strahlprojektionsabschnitt (130) zum Projizieren eines Strahls eines linear polarisierten Lichts in Richtung der ersten Probe;

- einen Polarisator (138), der den Durchgang eines Lichts mit einer bestimmten Polarisationsebene erlaubt;

- ein Umlenkprisma (170) zur Umlenkung des von der ersten Probe reflektierten Lichtstrahls parallel und in einem Abstand, um ihn zu der zweiten Probe zu lenken;

- einen Analysator (140), der den Durchgang eines Lichts mit einer bestimmten Polarisationsebene erlaubt; und

- einen Lichtdetektor (150) zum Erfassen eines durch den Analysator hindurch getretenen Lichts;

- wobei sich der erste Strahlengang von dem Strahlprojektionsabschnitt (130) über die erste Probe (114) zu dem Umlenkprisma (170) erstreckt, sich der zweite Strahlengang von dem Umlenkprisma (170) über die zweite Probe (124) zu dem Lichtdetektor (150) erstreckt, sich der erste und der zweite Strahlengang parallel und in einem Abstand zueinander erstrecken und miteinander durch das Umlenkprisma (170) verbunden sind;

- wobei der Polarisator (138) zwischen dem Strahlprojektionsabschnitt (130) und der ersten Probe (114) im ersten Strahlengang angeordnet ist, der Analysator (140) zwischen der zweiten Probe (124) und dem Lichtdetektor (150) im zweiten Strahlengang angeordnet ist, und der Polarisator (138) den Durchgang eines linear polarisierten Lichts erlaubt, dessen Polarisationsebene um einen Winkel von +45° gegenüber einer Einfallsebene der ersten Probe geneigt ist, wobei der Polarisator (138) und der Analysator (140) als gekreuztes Nicol'sches Prisma wirken;

- wobei eine (124) von der ersten und der zweiten Probe die Zielprobe, die weitere (114) von der ersten und der zweiten Probe die Referenzprobe ist, die bei der Polarisationsanalyse mit der Zielprobe verglichen wird, so dass eine (122) von der ersten und der zweiten Probenhaltereinheit eine Zielprobenhaltereinheit und die weitere (112) von der ersten und der zweiten Probenhaltereinheit eine Referenzprobenhaltereinheit ist;

- wobei das Ellipsometer ferner einen Probenpositionierungsmechanismus (310, 320, 330, 410, 420, 430) zur Anordnung der ersten und der zweiten Probe an geeigneten Positionen und in geeigneten Ausrichtungen umfasst, wobei der Probenpositionierungsmechanismus die Zielprobenhaltereinheit (122) umfasst, wobei die Zielprobenhaltereinheit die Zielprobe (124) hält, um deren Höhe und Neigung einzustellen, und wobei der Probenpositionierungsmechanismus einen Zielproben-Höhen/Neigungs-Einstellabschnitt (410, 420, 430) zur Einstellung der Höhe und der Neigung der Zielprobe umfasst;

- einen Polarisationswinkel-Einstellmechanismus (200), der zwischen dem Strahlprojektionsabschnitt (130) und dem Polarisator (138) angeordnet ist, um eine Winkelrichtung um eine optische Achse der Polarisation des von dem Strahlprojektionsabschnitt (130) projizierten linear polarisierten Lichts einzustellen, wobei der Polarisationswinkel-Einstellmechanismus (200) ein Linearpolarisationsdrehelement (202) zum Drehen der Polarisation eines einfallenden linear polarisierten Lichts um die optische Achse und eine Halterung (210) zum drehbaren Stützen des Linearpolarisationsdrehelements (202) um die optische Achse umfasst.

2. Ellipsometer nach Anspruch 1, wobei die Zielprobenhaltereinheit (122) einen Probenhalter (188), an dem die Zielprobe befestigt ist, einen ersten goniometrischen Träger zum Neigen des Probenhalters um eine erste Achse, einen zweiten goniometrischen Träger (194) zum Neigen des Probenhalters zusammen mit dem ersten goniometrischen Träger um eine zweite Achse und eine Höheneinstellvorrichtung (196) zum Verschieben des Probenhalters zusammen mit dem ersten und dem zweiten goniometrischen Träger entlang einer dritten Achse umfasst.

3. Ellipsometer nach Anspruch 2, wobei der Zielproben-Höhen/Neigungs-Einstellabschnitt eine optische Höhenmesseinheit (410), eine optische Neigungsmesseinheit (420) und einen Verarbeitungsabschnitt (430) zur Verarbeitung von Daten, die von der optischen Höhenmesseinheit und der optischen Neigungsmesseinheit gewonnen werden, umfasst, wobei die optische Höhenmesseinheit (410) einen Spiegel (412) zum bedarfsadaptiven Ablenken des Lichtstrahls, eine Drehvorrichtung (414) zum Bewegen des Spiegels zwischen einer Position, in der er den Strahlengang kreuzt, und einer Position abseits des Strahlengangs, und eine Kamera (416) zur Aufnahme eines Bildes des von dem Spiegel abgelenkten Lichtstrahls umfasst, und wobei die optische Neigungsmesseinheit (420) einen Spiegel (422) zum bedarfsadaptiven Ablenken des Lichtstrahls, eine Drehvorrichtung (424) zum Bewegen des Spiegels zwischen einer Position, in der er den Strahlengang kreuzt, und einer Position abseits des Strahlengangs, eine Objektivlinse (426) zum Konvergieren des von dem Spiegel abgelenkten Lichtstrahls, und eine Kamera (428) zur Aufnahme eines Bildes des durch die Objektivlinse konvergierten Lichtstrahls umfasst.

4. Ellipsometer gemäß Anspruch 3, wobei der Verarbeitungsabschnitt (430) einen Monitor zur Anzeige eines Punktes des Lichtstrahls in dem von der Kamera der optischen Höhenmesseinheit aufgenommenen Bild und zur Anzeige eines Bildes eines Punktes des konvergierten Lichtstrahls in dem von der Kamera der optischen Neigungsmesseinheit gewonnenen Bild umfasst.

5. Der Ellipsometer gemäß Anspruch 3, wobei der Verarbeitungsabschnitt (430) ein Mittel zur Ausführung arithmetischer Berechnungen, um Höhen/Neigungsdaten der Zielprobe zu gewinnen, ein Antriebsmittel zum Drehen einer Eingangsachse (192a) des ersten goniometrischen Trägers (192), einer Eingangsachse (194a) des zweiten goniometrischen Trägers (194) und einer Eingangsachse (162a) der Höheneinstellvorrichtung, und ein Steuerungsmittel zur Steuerung des Antriebsmittels auf der Grundlage der Höhen/Neigungsdaten umfasst.

6. Ellipsometer nach Anspruch 5, wobei das Mittel zur Ausführung arithmetischer Berechnungen Höhendaten dadurch gewinnt, dass ein Bild eines Punktes des Strahls in dem von der Kamera der optischen Höhenmesseinheit gewonnenen Bild in Binärform umgewandelt wird, um einen Schwerpunkt des Bildes des Punktes zu gewinnen, und Neigungsdaten auf der Grundlage einer Position eines Bildes des Punktes des konvergierten Strahls in dem von der Kamera der optischen Neigungsmesseinheit gewonnenen Bild gewinnt.

7. Ellipsometer nach einem der Ansprüche 1 bis 6, wobei der Probenpositionierungsmechanismus die Referenzprobenhaltereinheit (112) umfasst, wobei die Referenzprobenhaltereinheit die Referenzprobe (114) hält, um deren Höhe und Neigung einzustellen, und wobei der Probenpositionierungsmechanismus einen Referenzproben-Höhen/Neigungs-Einstellabschnitt (310, 320, 330) zur Einstellung der Höhe/Neigung der Referenzprobe enthält.

8. Ellipsometer nach Anspruch 7, wobei die Referenzprobenhaltereinheit (112) einen Probenhalter (182), an dem die Referenzprobe befestigt ist, einen ersten goniometrischen Träger (192) zum Neigen des Probenhalters um eine erste Achse, einen zweiten goniometrischen Träger (194) zum Neigen des Probenhalters zusammen mit dem ersten goniometrischen Träger um eine zweite Achse und eine Höheneinstellvorrichtung (196) zum Verschieben des Probenhalters zusammen mit dem ersten und dem zweiten goniometrischen Träger entlang einer dritten Achse.

9. Ellipsometer nach Anspruch 8, wobei der Referenzproben-Höhen/Neigungs-Einstellabschnitt eine optische Höhenmesseinheit (310), eine optische Neigungsmesseinheit (320) und einen Verarbeitungsabschnitt (330) zur Verarbeitung von Daten umfasst, die von der optischen Höhenmesseinheit und der optischen Neigungsmesseinheit gewonnen werden, wobei die optische Höhenmesseinheit (310) einen Spiegel (312) zum bedarfsadaptiven Ablenken des Lichtstrahls, eine Drehvorrichtung (314) zum Bewegen des Spiegels zwischen einer Position, in der er den Strahlengang kreuzt, und einer Position, die abseits vom Strahlengang liegt, und eine Kamera (316) zur Aufnahme eines Bildes von dem von dem Spiegel abgelenkten Lichtstrahl umfasst, und wobei die optische Neigungsmesseinheit (320) einen Spiegel (322) zur bedarfsadaptiven Ablenkung des Lichtstrahls, eine Drehvorrichtung (324) zum Bewegen des Spiegels zwischen einer Position, in der er den Strahlengang kreuzt, und einer Position, die abseits von dem Strahlengang liegt, eine Objektivlinse (326) zum Konvergieren des von dem Spiegel abgelenkten Lichtstrahls und eine Kamera (328) zur Aufnahme eines Bildes des durch die Objektivlinse konvergierten Lichtstrahls umfasst.

10. Ellipsometer nach Anspruch 9, wobei der Verarbeitungsabschnitt (330) einen Monitor zum Anzeigen eines Punktes des Lichtstrahls in dem von der Kamera der optischen Höhenmesseinheit gewonnenen Bild und zur Anzeige eines Bildes eines Punktes von dem konvergierten Lichtstrahl in dem von der Kamera der optischen Neigungsmesseinheit gewonnenen Bild umfasst.

11. Ellipsometer nach Anspruch 9, wobei der Verarbeitungsabschnitt (330) ein Mittel zur Ausführung arithmetischer Berechnungen, um Höhen- und Neigungsdaten der Referenzprobe zu gewinnen, ein Antriebsmittel zum Drehen einer Eingangsachse (192a) des ersten goniometrischen Trägers (192), einer Eingangsachse (194a) des zweiten goniometrischen Trägers und einer Eingangsachse (196a) der Höheneinstellvorrichtung (196), und ein Steuerungsmittel zur Steuerung des Antriebsmittels auf der Grundlage der Höhen- und Neigungsdaten umfasst.

12. Ellipsometer nach Anspruch 11, wobei das Mittel zur Ausführung arithmetischer Berechnungen Höhendaten durch Umwandeln eines Bildes eines Punktes des Lichtstrahls in dem von der Kamera der optischen Höhenmesseinheit gewonnenen Bild in Binärform gewinnt, um einen Schwerpunkt des Bildes des Punktes zu gewinnen, und Neigungsdaten auf der Grundlage einer Position eines Bildes des Punktes des konvergierten Lichtstrahls in dem von der Kamera der optischen Neigungsmesseinheit aufgenommenen Bild gewinnt.

13. Ellipsometer nach einem der Ansprüche 1 bis 12, wobei das Linearpolarisationsdrehelement (202) einen Halbwellenlängenplatte enthält.

14. Ellipsometer nach Anspruch 13, wobei die Halterung (210) die Halbwellenlängenplatte (202) so dreht, dass eine Winkelrichtung einer optischen Achse der Halbwellenlängenplatte innerhalb eines Bereichs von 0° bis 180° bezüglich der Polarisation des eintreffenden linear polarisierten Lichts verändert wird.

15. Ellipsometer nach einem der Ansprüche 1 bis 14, wobei die Halterung (210) einen beweglichen Rahmen (212) zum Halten des Linearpolarisationsdrehelements und einen festen Rahmen (214) zum drehbaren Stützen des beweglichen Rahmens um eine Achse (216), die mit der optischen Achse identisch ist, umfasst.

16. Ellipsometer nach Anspruch 15, wobei der feste Rahmen (214) einen Winkeleinstellmechanismus zur Einstellung eines Winkels des beweglichen Rahmens um die Achse umfasst, wobei der Winkeleinstellmechanismus eine drehbare Eingangsachse umfasst, wobei eine dieser zugeführte Drehung in eine Winkeländerung des beweglichen Rahmens umgewandelt wird.

17. Ellipsometer nach Anspruch 16, das ferner einen Steuerungsabschnitt (220) zur Steuerung des Winkeleinstellmechanismus umfasst, wobei der Steuerungsabschnitt ein Antriebsmittel zum Drehen der Eingangsachse des Winkeleinstellmechanismus, ein Erfassungsmittel zur Erfassung eines durch den Polarisator transmittierten Lichts und ein Steuerungsmittel zur Steuerung des Antriebsmittels auf der Grundlage eines Ausgangs von dem Erfassungsmittel, um einen maximalen Ausgang von dem Erfassungsmittel zu erhalten.

Revendications

1. Ellipsomètre (100) pour détecter une polarisation de lumière réfléchie successivement à partir d'un échantillon de référence et d'un échantillon cible, pour étudier un état de surface de l'échantillon cible, l'ellipsomètre, qui comporte un premier trajet optique et un second trajet optique, comprenant :

un premier module porte-échantillon (112) destiné à maintenir un premier échantillon (114) ;

un second module porte-échantillon (122) destiné à maintenir un second échantillon (124) ;

une partie de projection de faisceau (130) servant à projeter un faisceau d'une lumière polarisée dans un plan en direction du premier échantillon ;

un polariseur (138) destiné à laisser passer une lumière ayant un plan spécifique de polarisation ;

un prisme de retournement (170) destiné à retourner le faisceau de lumière réfléchi à partir du premier échantillon en parallèle sur une certaine distance dans le but de l'orienter vers le second échantillon ;

un analyseur (140) laissant passer la lumière ayant un plan spécifique de polarisation ; et

un détecteur de lumière (150) destiné à détecter la lumière laissée passée par l'analyseur,

le premier trajet optique s'étendant de la partie de projection de faisceau (130) vers le prisme de retournement (170) en passant par le premier échantillon (114), le second trajet optique s'étendant du prisme de retournement (170) vers le détecteur de lumière (150) en passant par le second échantillon (124), les premier et second trajets optiques s'étendant parallèlement avec un certain intervalle entre eux et étant mis en communication l'un avec l'autre par le prisme de retournement (170) ;

le polariseur (138) situé sur le premier trajet optique entre la partie de projection de faisceau (130) et le premier échantillon (114), l'analyseur (140) situé sur le second trajet optique entre le second échantillon (124) et le détecteur de lumière (150), le polariseur (138) laissant passer une lumière polarisée dans un plan ayant un plan de polarisation incliné à un angle de + 45° par rapport au plan d'incidence du premier échantillon, le polariseur (138) et l'analyseur (140) satisfaisant à des Nicols croisés ;

l'un (124) des premier et second échantillons étant l'échantillon cible, l'autre (114) des premier et second échantillons étant l'échantillon de référence à comparer avec l'échantillon cible lors d'une analyse de polarisation, par conséquent, l'un (122) des premier et second modules porte-échantillons étant un module porte-échantillon cible, l'autre (112) des premier et second modules porte-échantillons étant un module porte-échantillon de référence ;

un mécanisme de positionnement d'échantillons (310, 320, 330, 410, 420, 430) destiné à disposer les premier et second échantillons à des positions appropriées et dans des orientations appropriées, le mécanisme de positionnement d'échantillons comprenant le module porte-échantillon cible (122), le module porte-échantillon cible maintenant l'échantillon cible (124) de façon à en régler la hauteur et l'inclinaison, et le mécanisme de positionnement d'échantillons comprenant une section de réglage de hauteur/ d'inclinaison d'échantillon cible (410, 420, 430) servant à régler la hauteur et l'inclinaison de l'échantillon cible ; ledit ellipsomètre comprenant en outre :

un mécanisme de réglage angulaire de polarisation (200), agencé entre la partie de projection de faisceau (130) et le polariseur (138), servant à régler la direction angulaire de la polarisation d'une lumière polarisée dans un plan autour d'un axe optique projeté à partir de la partie de projection de faisceau (130), le mécanisme de réglage angulaire de polarisation (200) comprenant un élément rotatif de polarisation dans un plan (202) destiné à faire tourner la polarisation d'une lumière polarisée dans un plan incidente autour de l'axe optique, et un montage (210) destiné à supporter mobile en rotation l'élément rotatif de polarisation dans un plan (202) autour de l'axe optique.

2. Ellipsomètre selon la revendication 1, dans lequel le module porte-échantillon cible (122) comprend un porte-échantillon (182) sur lequel est fixé l'échantillon cible, une première platine goniométrique (192) destinée à incliner le porte-échantillon autour d'un premier axe, une seconde platine goniométrique (194) destinée à incliner le porte-échantillon, conjointement avec la première platine goniométrique, autour d'un deuxième axe, et une platine de réglage de hauteur (196) destinée à décaler le porte-échantillon, conjointement avec les première et seconde platines goniométriques, le long d'un troisième axe.

3. Ellipsomètre selon la revendication 2, dans lequel la section de réglage de hauteur/ d'inclinaison d'échantillon cible comprend un module optique de mesure de hauteur (410), un module optique de mesure d'inclinaison (420), et une section de traitement (430) servant à traiter des données obtenues à partir de chacun du module optique de mesure de hauteur et du module optique de mesure d'inclinaison ; le module optique de mesure de hauteur (410) comprenant un miroir (412) destiné à dévier le faisceau de lumière en fonction des besoins, un module rotatif (414) destiné à faire bouger le miroir entre une position coupant le trajet optique et une position hors du trajet optique, et un dispositif de prise de vue (416) destiné à prendre un cliché du faisceau de lumière réfléchi par le miroir ; et le module optique de mesure d'inclinaison (420) comprenant un miroir (422) destiné à dévier le faisceau de lumière en fonction des besoins, un module rotatif (424) destiné à faire bouger le miroir entre une position coupant le trajet optique et une position hors du trajet optique, une lentille d'objectif (426) destinée à faire converger le faisceau de lumière réfléchi par le miroir, et un dispositif de prise de vue (428) destiné à prendre un cliché du faisceau de lumière ayant fait l'objet d'une convergence par la lentille de convergence.

4. Ellipsomètre selon la revendication 3, dans lequel la section de traitement (430) comporte un écran destiné à afficher un point du faisceau de lumière dans le cliché obtenu par le dispositif de prise de vue du module optique de mesure de hauteur et à afficher une image d'un point du faisceau de lumière ayant fait l'objet d'une convergence dans le cliché obtenu par le dispositif de prise de vue du module optique de mesure d'inclinaison.

5. Ellipsomètre selon la revendication 3, dans lequel la section de traitement (430) comprend un moyen de calcul arithmétique destiné à obtenir des données de hauteur/ d'inclinaison de l'échantillon cible, un moyen d'entraînement destiné à faire tourner un axe d'entrée (192a) de la première platine goniométrique (192), un axe d'entrée (194a) de la seconde platine goniométrique (194), et un axe d'entrée (162a) de la platine de réglage de hauteur (196), et un moyen de commande destiné à commander le moyen d'entraînement sur les bases des données de hauteur/ d'inclinaison.

6. Ellipsomètre selon la revendication 5, dans lequel le moyen de calcul arithmétique obtient des données de hauteur par conversion d'une image d'un point du faisceau dans le cliché obtenu par le dispositif de prise de vue du module optique de mesure de hauteur en une forme binaire à des fins d'obtenir un centre de gravité de l'image du point, et obtient des données d'inclinaison sur la base d'une position d'une image du point du faisceau ayant fait l'objet d'une convergence dans le cliché obtenu par le dispositif de prise de vue du module optique de mesure d'inclinaison.

7. Ellipsomètre selon l'une quelconque des revendications 1 à 6, dans lequel le mécanisme de positionnement d'échantillons comprend le module porte-échantillon cible (112), le module porte-échantillon de référence maintenant l'échantillon de référence (114) de façon à en régler la hauteur et l'inclinaison, et le mécanisme de positionnement d'échantillons comprend une section de réglage de hauteur/ d'inclinaison d'échantillon de référence (310, 320, 330) servant à régler la hauteur/l'inclinaison de l'échantillon cible.

8. Ellipsomètre selon la revendication 7, dans lequel le module porte-échantillon de référence (112) comprend un porte-échantillon (182) sur lequel est fixé l'échantillon de référence, une première platine goniométrique (192) servant à incliner le porte-échantillon autour d'un premier axe, une seconde platine goniométrique (194) servant à incliner le porte-échantillon, conjointement avec la première platine goniométrique, autour d'un deuxième axe, et une platine de réglage de hauteur (196) servant à déplacer le porte-échantillon, conjointement avec les première et seconde platines goniométriques, le long d'un troisième axe.

9. Ellipsomètre selon la revendication 8, dans lequel la section de réglage de hauteur/ d'inclinaison d'échantillon de référence comprend un module optique de mesure de hauteur (310), un module optique de mesure d'inclinaison (320) et une section de traitement (330) destinée à traiter des données obtenues à partir de chacun du module optique de mesure de hauteur et du module optique de mesure d'inclinaison ; le module optique de mesure de hauteur (310) comprenant un miroir (312) destiné à dévier le faisceau de lumière en fonction des besoins, un module rotatif (314) destiné à faire bouger le miroir entre une position coupant le trajet optique et une position hors du trajet optique, et un dispositif de prise de vue (316) destiné à prendre un cliché du faisceau de lumière dévié par le miroir ; et le module optique de mesure d'inclinaison (320) comprenant un miroir (322) destiné à dévier le faisceau de lumière en fonction des besoins, un module rotatif (324) destiné à faire bouger le miroir entre une position coupant un trajet optique et une position hors du trajet optique, une lentille d'objectif (326) destinée à faire converger le faisceau de lumière dévié par le miroir, et un dispositif de prise de vue (328) destiné à prendre un cliché du faisceau de lumière ayant fait l'objet d'une convergence par la lentille d'objectif.

10. Ellipsomètre selon la revendication 9, dans lequel la section de traitement (330) comporte un écran destiné à afficher un point lumineux du faisceau de lumière dans le cliché obtenu par le dispositif de prise de vue du module optique de mesure de lumière et à afficher une image d'un point du faisceau de lumière ayant fait l'objet d'une convergence dans le cliché obtenu par le dispositif de prise de vue du module optique de mesure d'inclinaison.

11. Ellipsomètre selon la revendication 9, dans lequel la section de traitement (330) comprend un moyen de calcul arithmétique destiné à obtenir des données de hauteur et d'inclinaison de l'échantillon de référence, un moyen d'entraînement destiné à faire tourner un axe d'entrée (192a) de la première platine goniométrique (192), un axe d'entrée (194a) de la seconde platine goniométrique (194), et un axe d'entrée (196a) de la platine de réglage de hauteur (196), et un moyen de commande destiné à commander le moyen d'entraînement sur les bases des données de hauteur et d'inclinaison.

12. Ellipsomètre selon la revendication 11, dans lequel le moyen de calcul arithmétique obtient des données de hauteur par conversion d'une image d'un point du faisceau de lumière dans le cliché obtenu par le dispositif de prise de vue du module optique de mesure de hauteur en une forme binaire à des fins d'obtenir un centre de gravité de l'image du point, et obtient des données d'inclinaison sur la base d'une position d'une image du point du faisceau de lumière ayant fait l'objet d'une convergence dans le cliché obtenu par le dispositif de prise de vue du module optique de mesure d'inclinaison.

13. Ellipsomètre selon l'une quelconque des revendications 1 à 12, dans lequel l'élément rotatif de polarisation dans un plan (202) comprend une lame demi-onde.

14. Ellipsomètre selon la revendication 13, dans lequel le montage (210) fait tourner la lame demi-onde (202) de façon à faire varier une direction angulaire d'un axe optique de la lame demi-onde à l'intérieur d'une plage de 0° à 180° par rapport à la polarisation de la lumière polarisée dans un plan incidente.

15. Ellipsomètre selon l'une quelconque des revendications 1 à 14, dans lequel le montage (210) comprend un bâti mobile (212) servant à maintenir l'élément rotatif de polarisation dans un plan, et un bâti fixe (214) servant à supporter mobile rotation le bâti mobile autour d'un axe (216) identique à l'axe optique.

16. Ellipsomètre selon la revendication 15, dans lequel le bâti fixe (214) comprend un mécanisme de réglage angulaire servant à régler un angle du bâti mobile autour de l'axe, le mécanisme de réglage angulaire comportant un axe d'entrée tournant, une rotation qui lui est appliquée étant convertie en une variation angulaire du bâti mobile.

17. Ellipsomètre selon la revendication 16, comprenant en outre une section de commande (220) destinée à commander un mécanisme de réglage angulaire, la section de commande comprenant un moyen d'entraînement destiné à faire tourner l'axe d'entrée du mécanisme de réglage angulaire, un moyen de détection destiné à détecter une lumière passant par le polariseur, et un moyen de commande destiné à commander le moyen d'entraînement sur la base d'une sortie du moyen de détection de façon à obtenir une sortie maximale du moyen de détection.

Drawing